Anodic oxidation of organic substrates in the presence of nucleophiles

ABSTRACT

This invention refers to a process of anodic substitution comprising the electrolyzing the liquid reaction medium in an electrochemical cell comprising a cathode and an anode, whereas the liquid reaction medium comprises an organic compound with at least one carbon bound hydrogen atom, a nucleophilic agent, and an ionic liquid in a proportion of at least 10% by weight, and whereas the said hydrogen atoms are replaced at least partially with the nucleophilic group of said nucleophilic agent. Preferably, a gas diffusion layer electrode is used as anode.

This invention refers to a process of anodic substitution comprising electrolyzing the liquid reaction medium in an electrochemical cell comprising a cathode and an anode, whereas the liquid reaction medium comprises an organic compound with at least one carbon bound hydrogen atom, a nucleophilic agent, and an ionic liquid in a proportion of at least 10% by weight, and whereas the said hydrogen atoms are replaced at least partially with the nucleophilic group of said nucleophilic agent. In a preferred embodiment of the invention, a gas diffusion layer electrode is used as anode. Preferred nucleophilic agents are aliphatic alcohols and aliphatic carboxylic acids. Preferred ionic liquids are quaternary ammonium compounds having a melting point of less than 200° C. at atmospheric pressure (1 bar).

The anodic oxidation (in the context of this invention also referred to as electrochemical oxidation) of a substrate in the presence of nucleophile is an important reaction type in organic electrochemistry which allows for an anodic substitution. Different nucleophiles are used in this synthetic valuable electrolysis (Eberson & Nyberg, Tetrahedron 1976, 32, 2185). With alcanols like methanol an alkoxylation of a substrate can be carried out (EP 1348043 B, EP 1111094 A). With acids like HCOOH, CH₃COOH or CF₃COOH an acyloxylation of a substrate is possible (EP 1111094 A). Also the fluorination is known as one way for a selective introduction of fluorine. (Fuchigami, Organic Electrochemistry, 4th edn., (Eds.: Lund & Hammerich), Dekker, New York, 2001, p. 1035). In general this anodic substitution works nicely if the first step the removal of an electron from the substrate renders a stable enough cation radical so that an attack of a nucleophile can lead to the substituted product.

Anodic substitution is used at industrial scale for example in the double methoxylation of methylsubstituted aromatic compounds leading to the corresponding acetals. The first methoxylation step renders the ether as intermediate and the following methoxylation leads to the acetal in one cell/process. By this elegant way aromatic aldehydes are synthesized from toluene derivatives like p-tert-butyl benzaldehyde from p-tert-butyl toluene (DE 2848397).

But there are also drawbacks to this electrosynthesis which is shown for example in the limited substrate range for the acetalization of methylsubstituted aromatic compounds. The acetalization of p-substituted toluene derivatives is only successful if the substituent is electron pushing like the tert-butyl group in the industrial example above. Though if the p-substituent is non electron pushing the selectivity is very low. This problem was not solved in decades.

Also an obvious problem for an anodic substitution is if the reaction of the nucleophile with the substrate follows an undesired reaction path, e.g. cyclic compounds like ethylene carbonate react with nucleophiles under ring opening. Therefore a substitution at the ethylene carbonate ring generally has not been carried out by a nucleophilic but a radical pathway.

Unexpectedly, a method was found to improve anodic substitution in general (conversion rate, selectivity, current yield and accessibility of a broad range of organic compounds for anodic substitution) by use high ionic liquid electrolyte concentration.

This method also allows for anodic substitution of organic compounds which are prone to nucleophilic side reactions such as the ring-opening reaction of cyclic carbonates.

The invention provides a process of anodic substitution comprising the steps of:

-   a) providing an organic compound comprising at least one hydrogen     atom bound to a carbon atom; -   b) providing, in an electrochemical cell comprising a cathode and an     anode, a liquid reaction medium comprising the organic compound and     a nucleophilic agent; -   c) electrolyzing the liquid reaction medium to cause replacement of     at least a part of said hydrogen atoms with the nucleophilic group     of the nucleophilic agent, characterized in that the liquid reaction     medium additionally comprises ionic liquid in a proportion of at     least 10% by weight.

The process of anodic substitution is special case of electrochemical oxidation.

It is a critical feature of the process according to the invention to employ a liquid reaction medium that comprises ionic liquid in a proportion of at least 10% by weight.

In the context of the present invention, the term ionic liquid refers to salts (compounds of cations and anions) which at atmospheric pressure (1 bar) have a melting point of less than 200° C., preferably less than 150° C., particularly preferably less than 100° C.

Possible ionic liquids also include mixtures of different ionic liquids.

Preferred ionic liquids comprise an organic compound as cation (organic cation). Depending on the valence of the anion, the ionic liquid can comprise further cations, including metal cations, in addition to the organic cation. The cations of particularly preferred ionic liquids are exclusively an organic cation or, in the case of polyvalent anions, a mixture of different organic cations. Suitable organic cations comprise, in particular, heteroatoms such as nitrogen, sulfur, oxygen or phosphorus; in particular, the organic cations comprise an ammonium group (ammonium cations), an oxonium group (oxonium cations), a sulfonium group (sulfonium cations) or a phosphonium group (phosphonium cations).

In a particular embodiment, the organic cations of the ionic liquids are ammonium cations, which for the present invention are

-   -   non-aromatic compounds having a localized positive charge on the         nitrogen atom, e.g. compounds having tetravalent nitrogen         (quaternary ammonium compounds) or     -   compounds having trivalent nitrogen, with one bond being a         double bond, or     -   aromatic compounds having a delocalized positive charge and at         least one nitrogen atom, preferably from one to three nitrogen         atoms, in the aromatic ring system.

Preferred organic cations are quaternary ammonium cations, preferably those having three or four aliphatic substituents, particularly preferably C₁-C₁₂-alkyl groups, on the nitrogen atom; these aliphatic substituents may optionally be substituted by hydroxyl groups.

In the context of the present invention, the expression C₁-C₁₂-alkyl comprises straight-chain or branched and saturated or unsaturated C₁-C₁₂-alkyl groups. Preferably, the C₁-C₁₂-alkyl groups are saturated.

Preference is likewise given to organic cations which comprise a heterocyclic ring system having from one to three, in particular one or two, nitrogen atoms as constituents of the ring system. Monocyclic, bicyclic, aromatic or nonaromatic ring systems are all possible. Mention may be made by way of example of bicyclic systems as described in WO 2008/043837. The bicyclic systems of WO 2008/043837 are diazabicyclo derivatives, preferably formed by a 7-membered ring and a 6-membered ring, which comprise an amidinium group; particular mention may be made of the 1,8-diazabicyclo(5.4.0)undec-7-enium cation.

Particularly preferred ammonium cations are quaternary ammonium cations, imidazolium cations, pyrimidinium cations and pyrazolium cations.

The ionic liquids can comprise inorganic or organic anions. Such anions are described, for example, in the abovementioned WO 03/029329, WO 2007/076979, WO 2006/000197 and WO 2007/128268.

Preference is given to anions from the group of alkylsulfates of the formula R^(a)OSO₃ ⁻,

-   -   where R^(a) is a C₁-C₁₂-alkyl group, a perfluorinated         C₁-C₁₂-alkyl group, or a C₆-C₁₀-aryl group, preferably a         C₁-C₈-alkyl group, a perfluorinated C₁-C₆-alkyl group, or a         C₆-aryl group (tosylate);         alkylsulfonates of the formula R^(a)SO₃ ⁻,     -   where R^(a) is a C₁-C₁₂-alkyl group, preferably a C₁-C₆-alkyl         group;         bisalkylsulfonylimides of the formula (R^(a)SO₂)₂N⁻,     -   where R^(a) is a C₁-C₁₂-alkyl group or a perfluorinated         C₁-C₁₂-alkyl group, preferably a C₁-C₆-alkyl group or a         perfluorinated C₁-C₆-alkyl group;         halides, in particular chloride, bromide or iodide;         pseudohalides such as thiocyanate, dicyanamide;         carboxylates of the formula R^(a)COO⁻,     -   where R^(a) is a C₁-C₁₂-alkyl group, preferably a C₁-C₆-alkyl         group, in particular acetate; phosphates, in particular the         dialkyl phosphates of the formula R^(a)R^(b)PO₄ ⁻,     -   where R^(a) and R^(b) are each, independently of one another, a         C₁-C₆-alkyl group; in particular, R^(a) and R^(b) are the same         alkyl group (e.g. dimethyl phosphate or diethyl phosphate); and         phosphonates, in particular monoalkyl phosphonates of the         formula R^(a)PO₃ ⁻,     -   where R^(a) is a C₁-C₆-alkyl group.

Suitable ionic liquids in the context of the present invention are e.g. ammoniumtetraalkyl alkylsulfate (such as methyltributylammonium methylsulfate (MTBS)) or ammoniumtetraalkyl bis(alkylsulfonyl)imide (such as methyltributylammonium bis(trifluoromethylsulfonyl)imide (MTB-TFSI) or tetraoctylammonium bis(trifluoromethylsulfonyl)imide).

The proportion of the ionic liquid or the mixture thereof should be high at least 10% by weight, preferably at least 25% by weight, more preferably at least 50% by weight, particularly at least 65% by weight based on the entire liquid reaction medium.

As anode and cathode any electrode suitable for electrochemical oxidation processes can be used. A person skilled in the art can determine which electrode is suitable.

In a preferred embodiment of the invention, at least one gas diffusion layer electrode is employed as anode.

Gas diffusion layer (GDL) electrodes are known from fuel cell technology and consist of a substrate and a microporous layer containing carbon particles as main component. Suitable GDLs are described inter alia in U.S. Pat. No. 4,748,095, U.S. Pat. No. 4,931,168 and U.S. Pat. No. 5,618,392. The teaching of those documents is incorporated herein by reference. Suitable GDLs are commercial available e.g. from Ballard Power Systems Inc., Freudenberg FCCT KG (e.g. the g. of the H2315 series) or SGL Group.

A GDL generally comprises a fibre layer or substrate and a microporous layer (MPL) consisting of carbon particles attached to each other. The degree of hydrophobization can vary in such a way that wetting and gas permeability can be adjusted.

GDL electrodes for the process of the invention preferably do not contain a catalyst supported on the surface of the electrode.

GDL electrodes for the process of the invention contain a substrate and a microporous layer containing carbon particles preferable carbon black as main component.

GDL electrodes for the process of the invention can be manufactured according to U.S. Pat. No. 6,103,077, eventually using commercially available components like substrate and carbon particles.

Preferably, the cathode is selected from Pt, Pb, Ni, graphite, felt materials like coal or graphite felts, stainless steel and GDL electrodes.

The organic compound provided in step a) of process according to the present invention can generally be any organic compound that comprises at least one hydrogen atom directly bound to a carbon atom that can be substituted by a nucleophilic group under the conditions of the anodic substitution. It is of course also possible to employ a mixture of organic compounds. Suitable are organic compounds that in combination with at least one nucleophilic agent, with ionic liquid in a proportion of at least 10% by weight and optionally with solvents and/or additives allow the formation of a liquid reaction medium with ionic conductivity so that electrolysis can be applied to cause the anodic substitution.

Preferably, the hydrogen atom is directly bound to a carbon atom is part of an alkyl group, more preferably. According to the invention 1, 2 or 3 hydrogen atoms are directly bound to said carbon atom. Preferably, said carbon atom is a tertiary carbon atom of an alkane or a cycloalkane, an allylic carbon atom of an alkene or a cycloalkene or corresponding diens, a carbon atom in α-position to the arene moiety of an alkylarene, a carbon atom in α-position to the nitrogen atom of an amide, or a carbon atom in α-position to the oxygen atom of an ether.

Preferably, the organic compound according to the invention exhibits an alkyl or alkylen group having at least one hydrogen atom directly bound to a carbon atom. Particularly preferred organic compounds are (i) alkanes or cycloalkanes having at least one hydrogen atom directly bound to a tertiary carbon atom, (ii) alkenes or cycloalkenes or corresponding dienes having at least one hydrogen atom directly bound to an allylic carbon atom, (iii) alkylarenes having at least one hydrogen atom directly bound to a carbon atom in α-position to the arene moiety, (iv) amides having at least one hydrogen atom directly bound to a carbon atom in α-position to the nitrogen atom, or (v) ethers, esters, carbonates or acetals having at least one hydrogen atom directly bound to a carbon atom in α-position to the oxygen atom.

The organic compound can comprise functional groups that are essentially stable under the reaction conditions. Suitable functional groups comprise carbonyl, thiocarbonyl, ester, thioester, amide, oxycarbonyloxy, urethane, urea, hydroxyl, sulfonyl, sulfinate, sulfonate, sulfate, ether, amine, nitrile, etc. and combinations thereof.

In one embodiment of the present invention, the organic compound provided in step a) is selected from compounds of the general formula I

wherein

-   X is O, N—R³ or CR⁴R⁵, -   R¹ is selected from C₁-C₆-alkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl, formyl,     C₁-C₆-alkylcarbonyl and C₁-C₆-alkyloxycarbonyl,     -   wherein R¹ may also be C₁-C₆-alkoxy if X is a CR⁴R⁵ group,     -   wherein R¹ may also be C₁-C₆-alkylcarbonyloxy if X is a N—R³ or         CR⁴R⁵ group, -   R² is selected from hydrogen, C₁-C₆-alkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl,     C₆-C₁₀-aryl-C₁-C₆-alkyl, C₃-C₁₂-cycloalkyl and C₆-C₁₀-aryl, -   R³ is selected from hydrogen, C₁-C₆-alkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl,     formyl, C₁-C₆-alkylcarbonyl and C₁-C₆-alkyloxycarbonyl, -   R⁴ and R⁵ are independently selected from hydrogen, C₁-C₆-alkyl,     C₁-C₆-alkoxy-C₁-C₆-alkyl and C₁-C₆-alkoxy, -   or R¹ and R² together with the X—(C═O)—O group to which they are     bound form a 5- to 7-membered heterocyclic ring, which may contain     at least one additional heteroatom or heteroatom containing group,     selected from O, S, NR^(c) or C═O, wherein R^(e) is selected from     hydrogen, alkyl, cycloalkyl and aryl, -   or X is a CR⁴R⁵ group and R¹ and R⁴ together with the carbon atom to     which they are bound form a 3 to 7 membered carbocyclic ring.

Preferably, X is O, CH₂ or NR³, wherein R³ is C₁-C₄-alkyl or C₁-C₄-alkylcarbonyl.

In a preferred embodiment, R¹ and R² together with the X—(C═O)—O group to which they are bound form a 5 to 7 membered heterocyclic ring, which may contain at least one additional heteroatom or heteroatom containing group, selected from O, S, NR^(c) or CO═O, wherein R^(c) is selected from hydrogen, alkyl, cycloalkyl or aryl. In this embodiment, X is preferably O, CH₂ or NR³, wherein R³ is C₁-C₄-alkyl or C₁-C₄-alkylcarbonyl. Further, in this embodiment R¹ and R² together are selected from groups of the formulae —CH₂—CH₂—, —CH₂—CH₂—CH₂— and —CH(C_(x)H_(2x+1))—CH₂—, wherein x is 1, 2, 3 or 4.

In a further preferred embodiment, the organic compound provided in step a) is selected from compounds of the general formula Ia

wherein

-   X is O, CH₂ or NR³, wherein R³ is C₁-C₄-alkyl or     C₁-C₄-alkylcarbonyl, -   A is an alkylene group selected from —CH₂—, —CH₂—CH₂—,     —CH₂—CH₂—CH₂—, —CHR⁷—, —CHR⁷—CH₂—,     -   —CH₂—CHR⁷—, —CHR⁷—CH₂—CH₂—, —CH₂—CHR⁷—CH₂—, and —CH₂—CH₂—CHR⁷—,         wherein R⁷ is C₁-C₆-alkyl, -   R⁶ is hydrogen or C₁-C₆-alkyl.

Preferably, X is O or —CH₂—, A is —CH₂— or —CHR⁷—, wherein R⁷ is C₁-C₄-alkyl, and R⁶ is hydrogen or C₁-C₄-alkyl.

Examples of suitable organic compounds of the general formulas I and Ia are ethylene carbonate, propylene carbonate (4-methyl-1,3-dioxolan-2-one) and gamma butyrolactone.

In one embodiment of the present invention, the organic compound provided in step a) is selected from compounds of the general formula II

Z—CHR⁸R⁹  (II)

wherein

-   Z is selected from C₆-C₁₀-aryl, substituted C₆-C₁₀-aryl,     C₁-C₆-allyl, —NR¹⁰R¹¹ group, and C₁-C₆-alkoxy, -   R⁸ is selected from hydrogen, C₁-C₆-alkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl,     -   wherein R⁸ may also be C₁-C₆-alkoxy if Z is a C₆-C₁₀-aryl or         C₁-C₆-allyl, -   R⁹ is selected from hydrogen, C₁-C₆-alkyl, C₁-C₆-alkoxy,     C₁-C₆-alkoxy-C₁-C₆-alkyl, C₆-C₁₀-aryl, substituted C₆-C₁₀-aryl,     C₆-C₁₀-aryl-C₁-C₆-alkyl, and C₃-C₁₂-cycloalkyl, or -   R⁸ and R⁹ together form a C₄-C₁-alkylen or a C₄-C₇-alkenylen, and     -   R¹⁰ and R¹¹ are independently selected from hydrogen,         C₁-C₆-alkyl, C₆-C₁₀-aryl, substituted C₆-C₁₀-aryl, and         C₁-C₆-alkylcarbonyl         or wherein -   Z, R⁸ and R⁹ are independently a C₁-C₆-alkyl.

Preferably, Z is C₆-C₁₀-aryl or substituted C₆-C₁₀-aryl, and R⁸ and R⁹ are independently selected from hydrogen, C₁-C₆-alkyl and C₁-C₆-alkoxy, particularly preferably, Z is C₆-C₁₀-aryl or substituted C₆-C₁₀-aryl, and R⁸ and R⁹ are independently selected from hydrogen, C₁-C₄-alkyl and C₁-C₄-alkoxy.

Also preferably, Z is C₁-C₆-alkoxy, R⁸ is selected from hydrogen and C₁-C₆-alkyl, and R⁹ is selected from hydrogen, C₁-C₆-alkyl, C₁-C₆-alkoxy, C₆-C₁₀-aryl, and substituted C₆-C₁₀-aryl, particularly preferably, Z is C₁-C₄-alkoxy, R⁸ is selected from hydrogen and C₁-C₄-alkyl, and R⁹ is selected from hydrogen, C₁-C₄-alkyl, C₁-C₄-alkoxy, C₆-C₁₀-aryl, and substituted C₆-C₁₀-aryl.

Examples of suitable organic compounds of the general formula II are toluene, benzyl methyl ether and benzaldehyde dimethylacetal.

In the context of the present invention, the expression C₁-C₆-alkyl comprises straight-chain or branched and saturated or unsaturated C₁-C₆-alkyl groups. Preferably, the C₁-C₆-alkyl groups are saturated. Examples of C₁-C₆-alkyl groups are methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, neo-pentyl and n-hexyl.

The above remarks regarding alkyl also apply to the alkyl moiety in alkoxy.

In the context of the present invention, the term “cycloalkyl” denotes a cycloaliphatic radical having usually from 3 to 12 carbon atoms, preferably 5 to 8 carbon atoms, such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, norbornyl, bicyclo[2.2.2]octyl or adamantyl.

In the context of the present invention, the term C₆-C₁₀-aryl refers to mono- or polycyclic aromatic hydrocarbon radicals. C₆-C₁₀-aryl is preferably phenyl or naphthyl.

In the context of the present invention, the term substituted C₆-C₁₀-aryl refers to mono- or polycyclic aromatic hydrocarbon radicals having 1 to 3 aromatic hydrogen atoms, preferably having 1 hydrogen atom substituted. Preferably, the substituents are independently selected from C₁-C₆-alkyl and C₁-C₆-alkoxy. Preferably, the substituent is in p-position. Examples of such substituents are p-methoxy, p-t-butyl or p-methyl.

In step b) of the process according to the invention, a liquid reaction medium comprising ionic liquid in a proportion of at least 10% by weight, the organic compound and a nucleophilic agent is provided.

The nucleophilic agent employed in step b) can be any agent or mixtures of agents which provides a nucleophile which is stabile under the electrolysis conditions and which is capable to substitute a hydrogen atom of the organic compound with a nucleophilic group during the anodic substitution.

A general formula for the anodic substitution according to the invention is

R—H+Nu⁻→R—Nu+H⁺+2e ⁻,

whereas R—H is the organic compound as specified above and Nu⁻ is the nucleophile. Importantly, the left side of this formula contains two species that would not react with each other where it not for the fact that two electrons are removed from the system.

The nucleophile represented by Nu⁻ is not necessarily negatively charged. A nucleophile in the context of the invention may also be e.g. pyridine (C₅H₅N). In such a case a positively charged substitution product is gained.

Nucleophilic agents in the context of the present invention are compounds which possess a nucleophilic group. The nucleophilic group or the nucleophilic agent itself can act as nucleophile in a nucleophilic substitution reaction with the organic compound having at least one hydrogen atom bound to an electrophilic carbon atom. In the course of the nucleophilic substitution reaction said hydrogen atom is replaced with the nucleophilic group. In certain cases the nucleophilic group is identical to the nucleophilic agent (e.g. pyridine (C₅H₅N)). In the context of the present invention, the term nucleophile refers to the attacking agent (e.g. C₅H₅N, RO⁻ and RCOO⁻, but also ROH, RCOOH), whereas the term nucleophilic group refers to the replacement group (e.g. RO⁻ or RCOO⁻ but not ROH or RCOOH).

Preferred nucleophiles of the present invention are selected from the group consisting of HO⁻, RO⁻, ROH, RCOO⁻, RCOOH, NO₂ ⁻, NO₃ ⁻, N₃ ⁻, OCN⁻, SCN⁻, RSO₃ ⁻, SeCN⁻, CN⁻, Cl⁻, Br, and I⁻, whereas R represents an alkyl or any group, preferably an alkyl group. Particularly preferred nucleophiles of the present invention are RO⁻, ROH, RCOO⁻, or RCOOH.

Anodic substitutions employing the nucleophiles HO⁻, RO⁻, RCOO⁻, or NO₃ ⁻ result in the formation of C—O bonds:

-   -   R—H+R′COO⁻→R—OCOR′+H⁺+2 e⁻ (anodic acyloxylation)     -   R—H+R′O⁻→R—OR′+H⁺+2 e⁻ (anodic alkoxylation)     -   R—H+HO⁻→R—OH+H⁺+2 e⁻ (anodic hydroxylation)     -   R—H+NO₃ ⁻→R—ONO₂+H⁺+2 e⁻ (anodic nitratation)     -   R—H+R′SO₃ ⁻→R—OSO₂R′+H⁺+2 e⁻

Anodic substitutions employing the nucleophiles N₃ ⁻, OCN⁻, or NO₂ ⁻ result in the formation of C—N bonds:

-   -   R—H+N₃ ⁻→R—N₃+H⁺+2 e⁻ (anodic azidation)     -   R—H+OCN⁻→R—NCO+H⁺+2 e⁻     -   R—H+NO₂ ⁻→R—NO₂+H⁺+2 e⁻ (anodic nitration)

Anodic substitution employing the nucleophile CN⁻ results in the formation of a C—C bond:

-   -   R—H+CN⁻→R—CN+H⁺+2 e⁻ (anodic cyanation)

Nucleophilic agents in the context of the present invention are compounds which possess a nucleophilic group, e.g. water (with the nucleophilic group HO⁻), alcohols (e.g. of the formula ROH with the nucleophilic group RO⁻), carboxylic acids (e.g. of the formula RCOOH with the nucleophilic group RCOO⁻), nitrous acid or salts thereof (with the nucleophilic group NO₂), nitric acid or salts thereof (with the nucleophilic group NO₃ ⁻), hydrazoic acid or salts thereof (with the nucleophilic group N₃ ⁻), isocyanic acid or salts thereof (with the nucleophilic group OCN⁻), isothiocyanic acid or salts thereof (with the nucleophilic group SCN⁻), sulfonic acid (e.g. of the formula RSO₃H with the nucleophilic group RSO₃ ⁻), isoselenocyanic acid or salts thereof (with the nucleophilic group SeCN⁻), hydrogen cyanide or salts thereof (with the nucleophilic group CN⁻), hydrogen chloride or salts thereof (with the nucleophilic group Cl⁻), hydrogen bromide or salts thereof (with the nucleophilic group Br⁻), or hydrogen iodide or salts thereof (with the nucleophilic group I⁻), whereas R represents an alkyl or arly group, preferably an alkyl group. Preferred nucleophilic agents of the present invention are alcohols of the formula III

R¹²OH  (III)

or carboxylic acids of the formula IV

R¹³COOH  (IV),

where R¹² and R¹³ are C₁-C₁₂-alkyl or C₁-C₁₂-perfluorinated alkyl, preferably C₁-C₆-alkyl or C₁-C₆-perfluorinated alkyl, particular preferably C₁-C₆-alkyl.

In a particular embodiment of the invention, F⁻ is excluded from the nucleophiles. Accordingly, in this particular embodiment, F⁻ providing compounds (fluorinating agents) are excluded from the nucleophilic agents. Also in this particular embodiment, such fluorinating agents are excluded from the ionic liquids.

The molar ratio of nucleophilic agent (with regard nucleophilic group) to organic compound is preferably in the range from 1:1 to 99:1 (nucleophilic agent:organic compound), more preferably from 2:1 to 99:1.

In a particular embodiment of the invention, the organic compound provided in step a) is selected from compounds of the general formula V

Y—CH₂R¹⁴  (V)

wherein

-   Y is selected from C₆-C₁₀-aryl, substituted C₆-C₁₀-aryl,     C₁-C₆-allyl, and —NR¹⁰R¹¹ group, -   R¹⁴ is selected from hydrogen, C₁-C₆-alkyl,     C₁-C₆-alkoxy-C₁-C₆-alkyl, C₆-C₁₀-aryl-C₁-C₆-alkyl, C₆-C₁₀-aryl,     substituted C₆-C₁₀-aryl and C₃-C₁₂-cycloalkyl, -   R¹⁰ and R¹¹ are specified as above,     and the nucleophilic agent is an alcohol of the formula III as     specified above,     whereas in the course of the anodic substitution process two     hydrogen atoms are subsequently replaced by —OR¹² groups resulting     in an acetal of the formula VI

γY—C(OR¹²)₂R¹⁴  (VI).

In one embodiment, the invention provides a process of manufacturing an acetal of the general formula VI as specified above by anodic substitution comprising the steps of:

-   a) providing an organic compound of the general formula V as     specified above; -   b) providing, in an electrochemical cell comprising a cathode and an     anode, a liquid reaction medium comprising the organic compound and     an alcohol of the general formula III as specified above; -   c) electrolyzing the liquid reaction medium to cause the formation     of the acetal of the general formula VI,     characterized in that the liquid reaction medium additionally     comprises ionic liquid in a proportion of at least 10% by weight.

Preferably, at least one gas diffusion layer electrode is employed as anode.

An example for such an acetalization process is the conversion of toluene with methanol to benzaldehyde dimethylacetal.

In a particular embodiment of the invention, the organic compound provided in step a) is selected from compounds of the general formula V

Y—CH₂R¹⁴  (V)

wherein

-   Y is selected from C₆-C₁₀-aryl, substituted C₆-C₁₀-aryl,     C₁-C₆-allyl, and —NR¹⁰R¹¹ group, -   R¹⁴ is selected from hydrogen, C₁-C₆-alkyl,     C₁-C₆-alkoxy-C₁-C₆-alkyl, C₆-C₁₀-aryl-C₁-C₆-alkyl, C₆-C₁₀-aryl,     substituted C₆-C₁₀-aryl and C₃-C₁₂-cycloalkyl, -   R¹⁰ and R¹¹ are specified as above,     and the nucleophilic agent is an alcohol of the formula III as     specified above,     whereas in the course of the anodic substitution process two     hydrogen atoms are subsequently replaced by —OR¹² groups resulting     in an acetal of the formula VI

Y—C(OR¹²)₂R¹⁴  (VI), and

whereas the acetal of formula VI is subsequently hydrolysed resulting in an aldehyde or ketone of formula Via

Y—COR¹⁴  (VIa).

In one embodiment, the invention provides a process of manufacturing an aldehyde or ketone of the general formula VIa as specified above by anodic substitution comprising the steps of:

-   a) providing an organic compound of the general formula V as     specified above; -   b) providing, in an electrochemical cell comprising a cathode and an     anode, a liquid reaction medium comprising the organic compound and     an alcohol of the general formula III as specified above; -   c) electrolyzing the liquid reaction medium to cause the formation     of the acetal of the general formula VI; -   d) hydrolyzing the acetal of the general formula VI to cause the     formation of the aldehyde or ketone of the general formula VIa,     characterized in that the liquid reaction medium additionally     comprises ionic liquid in a proportion of at least 10% by weight.

Preferably, at least one gas diffusion layer electrode is employed as anode.

An example for such a manufacturing process is the conversion of toluene with methanol to benzaldehyde dimethylacetal and the subsequent hydrolysis of the benzaldehyde dimethylacetal to benzaldehyde. Hydrolysis step can be performed according to protocols known by the skilled person.

In the context of the present invention, the expression “liquid reaction medium” denotes a reaction medium that comprises a liquid phase under the reaction conditions of the anodic substitution. This liquid phase contains a sufficient amount of the organic compound to allow anodic substitution. It is not necessary that the liquid phase contains the organic compound in form of a homogeneous solution, as long as a sufficient amount of the organic compound is brought in contact with the electrodes of the electrochemical cell, in particular the anode. Thus, the liquid reaction medium may contain the organic compound in form of a homogeneous solution, colloidal solution, molecularly disperse solution, emulsified phase or disperse phase. Finally, it is also possible to introduce a gaseous stream containing the organic compound into the liquid reaction medium.

The liquid reaction medium within the electrochemical oxidation cell comprises ionic liquid in a proportion of at least 10% by weight based on the total liquid reaction medium, an amount of organic compound solubilized therein, and an amount of nucleophilic agent solubilized therein. The process according to the invention does not require any additional solvents or additives to establish a anodic substitution reaction with high conversion rates and good selectivity. In particular, the ionic liquid employed also function as conducting salt (electrolyte).

In one embodiment of the present invention, the liquid reaction medium comprises in essence no additional solvents or other additives, i.e. the proportion of solvents and other additives is below 1% by weight, based on the total weight of the liquid reaction medium.

If the liquid reaction medium contains an organic solvent, it is preferably selected from acetonitrile, ethers, halogenated alkanes, sulfolane and mixtures thereof.

In a specific embodiment of the present invention the liquid reaction medium comprises at least one further additive as redox mediator and/or supportive electrolyte.

Redox mediators are used in indirect electrolyses. Typical examples of redox mediators are 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO), triarylamines such as tris(2,4-dibromophenyl)amine or halogenides such as bromide or iodide (Steckhan, Angewandte Chemie 1986, 98,681-699).

In the present invention preferred redox mediators are bromide or iodide salts, particular bromide salts such as alkaline bromide salts or tetraalkylammonium bromide salts.

In a specific embodiment of the present invention the liquid reaction medium comprises a bromide or iodide salt as further additive. Preferably, in this specific embodiment a GDL electrode is employed as anode and the ionic liquid is employed in a proportion of from 30 to 70% by weight, preferably from 40 to 50% by weigh based on the entire liquid reaction medium. Preferably, in this specific embodiment the organic compound provided in step a) is selected from compounds of the general formula VII

Y—CR¹⁵2H  (VII)

wherein Y is specified as above, R¹⁵ is a C₁-C₁₂-alkoxy, preferably a C₁-C₆-alkoxy, and the nucleophilic agent is an alcohol of the formula III as specified above, whereas in the course of the anodic substitution process the hydrogen atom is replaced by the —OR¹⁰ group resulting in an ortho-ester of the formula VIII

Y—CR¹⁵ ₂(OR¹²)  (VIII).

In one embodiment, the invention provides a process of manufacturing an ortho-ester of the general formula VIII as specified above by anodic substitution comprising the steps of:

-   a) providing an organic compound of the general formula VII as     specified above; -   b) providing, in an electrochemical cell comprising a cathode and an     anode, a liquid reaction medium comprising the organic compound, a     bromide or iodide salt, and an alcohol of the general formula III as     specified above; -   c) electrolyzing the liquid reaction medium to cause the formation     of the acetal of the general formula VII,     characterized in that the liquid reaction medium additionally     comprises ionic liquid in a proportion of at least 10% by weight.

Preferably, at least one gas diffusion layer electrode is employed as anode.

Such a process of mediated alkoxylation of an acetal to the ortho-ester is improved compared to the mediated alkoxylation processes concerning the current yield reported within the prior art (Grosse Brinkhaus et al., Tetrahedron, 1986, 42, 553-560).

In one embodiment of the invention, the organic compound provided in step a) is a compound of the general formula Ia as specified above and the nucleophilic agent is a carboxylic acids of the formula (IV) as specified above. Preferably, the nucleophilic acid within this embodiment is a carboxylic acid of the formula IV, wherein R¹³ is C₄-C₁₂-alkyl, preferably C₄-C₆-alkyl having a tertiary carbon atom in alpha position. This process of the invention allows for the anodic substitution of an organic compound of formula Ia such as e.g. ethylene carbonate or propylene carbonate with a carboxylic acid (acyloxylation) which is very surprisingly related to the easy ring-opening of ethylene carbonate with nucleophiles even if acids are mediocre nucleophiles. Accordingly, in one embodiment, the invention provides a process of manufacturing an acyloxylated organic compound of the general formula Ib

wherein X, A, and R⁶ are specified as above in the context of the general formula Ia and wherein R¹³ is C₁-C₁₂-alkyl or C₁-C₁₂-perfluorinated alkyl, preferably C₁-C₆-alkyl or C₁-C₆-perfluorinated alkyl, particular preferably C₄-C₆-alkyl having a tertiary carbon atom in α-position by anodic substitution comprising the steps of:

-   a) providing an organic compound of the general formula Ia as     specified above; -   b) providing, in an electrochemical cell comprising a cathode and an     anode, a liquid reaction medium comprising the organic compound and     an carboxylic acid of the general formula IV as specified above; -   c) electrolyzing the liquid reaction medium to cause the formation     of the acyloxylated organic compound of the general formula Ib,     characterized in that the liquid reaction medium additionally     comprises ionic liquid in a proportion of at least 10% by weight.

An overview on the construction possibilities of electrolysis cells that are suitable as electrochemical oxidation cells for the process of the invention can be found, for example, in Pletcher & Walsh, Industrial Electrochemistry, 2nd Edition, 1990, London, pp. 60ff.

Suitable electrochemical cells for the electrochemical oxidation are undivided cells and divided cells. An undivided cell usually comprises only one electrolyte portion; a divided cell has two or more such portion. The individual electrodes can be connected in parallel (monopolar) or serially (bipolar). In a suitable embodiment, the electrochemical cell employed for the electrochemical oxidation is a monopolar cell comprising a GDL anode and a cathode. In a further suitable embodiment, the electrochemical cell employed for the electrochemical oxidation is a cell having bipolar connection of the stacked electrodes.

In a preferred embodiment, the electrochemical oxidation cell is a plate-and-frame cell. Plate-and-frame cells employed in the process of the invention preferably comprise at least one GDL electrode. This type of cell is composed essentially of usually rectangular electrode plates and frames which surround them. They can be made of polymer material, for example polyethylene, polypropylene, polyvinyl chloride, polyvinylidene fluoride, PTFE, etc. The electrode plate and the associated frame are frequently joined to each other to form an assembly unit. By pressing a plurality of such plate-and-frame units together, a stack which is assembled according to the constructional fashion of filter presses is obtained. Yet further frame units, for example for receiving spacing gauzes, etc. can be inserted in the stack.

The process according to the invention can be performed according to known methods for the anodic substitution by electrolyzing the liquid reaction medium in order to cause replacement of at least a part of the carbon bound hydrogen atoms with nucleophilic groups, with the proviso that the employed liquid reaction medium comprises ionic liquid in a proportion of at least 10% by weight.

One or more anodes and one or more cathodes are placed in the liquid reaction medium. According to the invention, preferably at least the anode is a GDL electrode. An electric potential (voltage) is established between the anode(s) and cathode(s), resulting in an oxidation reaction (anodic substitution, i.e., replacement of one or more carbon bound hydrogen atoms with carbon bound nucleophilic groups) at the anode, and a reduction reaction (primarily hydrogen evolution) at the cathode.

Preferably, the anodic substitution reaction is performed with a constant current applied; i.e. at a constant voltage and a constant current flow. It is of course also possible, to interrupt the electric current through a current cycle, as described in U.S. Pat. No. 6,267,865.

The current density applied in step c) is in ranges known to the expert. Preferably, the current density employed in step c) is in a range of from 10 to 250 mA/cm², more preferably, in the range of from 10 to 100 mA/cm².

The anodic substitution products can be separated from the reaction medium by customary methods, preferably by distillation. The distillation of the reaction discharge can be carried out by customary methods known to those skilled in the art. Suitable apparatuses for the fractionation by distillation comprise distillation columns such as tray columns, which can be provided with bubble caps, sieve plates, sieve trays, packings, internals, valves, side offtakes, etc. Dividing wall columns, which may be provided with side offtakes, recirculations, etc., are especially suitable. A combination of two or more than two distillation columns can be used for the distillation. Further suitable apparatuses are evaporators such as thin film evaporators, falling film evaporators, Sambay evaporators, etc, and combinations thereof.

The use of a liquid reaction medium which comprises ionic liquid in a proportion of at least 10% by weight in the process of the invention has a positive effect on at least one of the following parameters: selectivity of the nucleophilic substitution, conversion rate of the nucleophilic substitution reaction, current yield, space-time yield, service life of the cell, and accessibility of a broad range of organic compounds for anodic substitution. This positive effect is even more pronounced if additionally a GDL electrode is used as anode. While not being bound to any theory it is assumed, that intermediates of the nucleophilic substitution reaction of the organic compound, e.g. cation-radicals generated during the anodic oxidation step, are stabilized by the ionic liquid and that this stabilization is even better if the ionic liquid is used in combination with a GDL anode.

EXAMPLES

The following examples are intended for further illustration of the present invention.

Example 1 for Comparison

In a 100 ml undivided electrolysis cell 6.5 g toluene, 34.1 g methanol and 2.6 g methyltributylammonium methylsulfate (MTBS, 6% by weight) as supporting electrolyte were electrolyzed for 7 F using a graphite anode (10 cm²) and a stainless steel cathode (10 cm²). The applied current density was 34 mA/cm². The GC analysis showed 65% conversion of toluene, a selectivity to benzaldehyde dimethylacetal of 7% and a current yield of 2%. The results of this experiment are summarized in table 1.

Example 2

In a 100 ml undivided electrolysis cell 7.5 g toluene, 17.0 g methanol and 25.5 g methyltributylammonium methylsulfate (MTBS, 51% by weight) as supporting electrolyte were electrolyzed for 7 F using a graphite anode (10 cm²) and a stainless steel cathode (10 cm²). The applied current density was 34 mA/cm². The GC analysis showed 88% conversion of toluene, a selectivity to benzaldehyde dimethylacetal of 32% and a current yield of 15%. The results of this experiment are summarized in table 1.

Example 3

In a 100 ml undivided electrolysis cell 13.1 g toluene, 29.5 g methanol and 9.8 g methyltributylammonium methylsulfate (MTBS, 12% by weight) as supporting electrolyte were electrolyzed for 7 F using a GDL (10 cm²) as anode and a stainless steel cathode (10 cm²). The current density was 34 mA/cm². The GC analysis showed 87% conversion of toluene, a selectivity to benzaldehyde dimethylacetal of 22% and a current yield of 9%. The GDL electrode has been be manufactured according to U.S. Pat. No. 6,103,077 using carbon black. The results of this experiment are summarized in table 1.

Example 4

In a 100 ml undivided electrolysis cell 13.1 g toluene, 29.5 g methanol and 9.8 g methyltributylammonium methylsulfate (MTBS, 25% by weight) as supporting electrolyte were electrolyzed for 7 F using a GDL (10 cm²) as anode and a stainless steel cathode (10 cm²). The current density was 34 mA/cm². The GC analysis showed 89% conversion of toluene, a selectivity to benzaldehyde dimethylacetal of 29% and a current yield of 13%. The GDL electrode has been be manufactured according to U.S. Pat. No. 6,103,077 using carbon black. The results of this experiment are summarized in table 1.

Example 5

In a 100 ml undivided electrolysis cell 13.1 g toluene, 29.5 g methanol and 9.8 g methyltributylammonium methylsulfate (MTBS, 51% by weight) as supporting electrolyte were electrolyzed for 8 F using a commercial GDL (H2315 IX11CX45 from Freudenberg, 10 cm²) as anode and a stainless steel cathode (10 cm²). The current density was 34 mA/cm². The GC analysis showed 98% conversion of toluene, a selectivity to benzaldehyde dimethylacetal of 45% and a current yield of 21%. The results of this experiment are summarized in table 1.

Example 6

In a 100 ml undivided electrolysis cell 7.9 g toluene, 17.9 g methanol and 26.9 g methyltributylammonium methylsulfate (MTBS, 51% by weight) as supporting electrolyte were electrolyzed for 7 F using a commercial GDL (Sigracet GDL 25 BC from SGL Group, 10 cm²) as anode and a stainless steel cathode (10 cm²). The current density was 34 mA/cm². The GC analysis showed 96% conversion of toluene, a selectivity to benzaldehyde dimethylacetal of 45% and a current yield of 23%. The results of this experiment are summarized in table 1.

Example 7

In a 100 ml undivided electrolysis cell 7.6 g toluene, 17.2 g methanol and 25.8 g methyltributylammonium methylsulfate (MTBS, 51% by weight) as supporting electrolyte were electrolyzed for 6 F using a GDL (10 cm²) as anode and a stainless steel cathode (10 cm²). The current density was 34 mA/cm². The GC analysis showed 97% conversion of toluene, a selectivity to benzaldehyde dimethylacetal of 48% and a current yield of 25%. The GDL electrode has been be manufactured according to U.S. Pat. No. 6,103,077 using carbon black. The results of this experiment are summarized in table 1.

Example 8

In a 100 ml undivided electrolysis cell 8.1 g toluene, 18.3 g methanol and 27.4 g methyltributylammonium methylsulfate (MTBS, 51% by weight) as supporting electrolyte were electrolyzed for 6 F using a GDL (10 cm²) as anode and a stainless steel cathode (10 cm²). The current density was 65 mA/cm². The GC analysis showed 94% conversion of toluene, a selectivity to benzaldehyde dimethylacetal of 49% and a current yield of 27%. The GDL electrode has been be manufactured according to U.S. Pat. No. 6,103,077 using carbon black. The results of this experiment are summarized in table 1.

Example 9

In a 100 ml undivided electrolysis cell 4.9 g toluene, 10.9 g methanol and 36.8 g methyltributylammonium methylsulfate (MTBS, 70% by weight) as supporting electrolyte were electrolyzed for 6 F using a graphite anode (10 cm²) and a stainless steel cathode (10 cm²). The applied current density was 34 mA/cm². The GC analysis showed 81% conversion of toluene, a selectivity to benzaldehyde dimethylacetal of 30% and a current yield of 15%. The results of this experiment are summarized in table 1.

Example 10

In a 100 ml undivided electrolysis cell 5.2 g toluene, 11.7 g methanol and 39.4 g methyltributylammonium methylsulfate (MTBS, 70% by weight) as supporting electrolyte were electrolyzed for 6 F using a GDL (10 cm²) as anode and a stainless steel cathode (10 cm²). The current density was 34 mA/cm². The GC analysis showed 93% conversion of toluene, a selectivity to benzaldehyde dimethylacetal of 50% and a current yield of 28%. The GDL electrode has been be manufactured according to U.S. Pat. No. 6,103,077 using carbon black. The results of this experiment are summarized in table 1.

Example 11

In a 100 ml undivided electrolysis cell 5.9 g toluene, 13.2 g methanol and 44.4 g 1-Ethyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide (EMimid-TFSI, 70% by weight) as supporting electrolyte were electrolyzed for 6 F using a GDL (10 cm²) as anode and a stainless steel cathode (10 cm²). The applied current density was 34 mA/cm². The GC analysis showed 98% conversion of toluene, a selectivity to benzaldehyde dimethylacetal of 50% and a current yield of 30%. The GDL electrode has been be manufactured according to U.S. Pat. No. 6,103,077 using carbon black. The results of this experiment are summarized in table 1.

Example 12

In a 100 ml undivided electrolysis cell 5.6 g toluene, 12.7 g methanol and 42.8 g methyltributylammonium bis(trifluoromethylsulfonyl)imide (MTB-TFSI, 70% by weight) as supporting electrolyte were electrolyzed for 6 F using a GDL (10 cm²) as anode and a stainless steel cathode (10 cm²). The applied current density was 34 mA/cm². The GC analysis showed 98% conversion of toluene, a selectivity to benzaldehyde dimethylacetal of 50% and a current yield of 32%. The GDL electrode has been be manufactured according to U.S. Pat. No. 6,103,077 using carbon black. The results of this experiment are summarized in table 1.

Example 13

In a 100 ml undivided electrolysis cell 6.0 g toluene, 13.5 g methanol and 45.4 g methyltributylammonium bis(trifluoromethylsulfonyl)imide (MTB-TFSI, 70% by weight) as supporting electrolyte were electrolyzed for 5.5 F using a GDL (10 cm²) as anode and a stainless steel cathode (10 cm²). The applied current density was 60 mA/cm². The GC analysis showed 95% conversion of toluene, a selectivity to benzaldehyde dimethylacetal of 54% and a current yield of 35%. The GDL electrode has been be manufactured according to U.S. Pat. No. 6,103,077 using carbon black. The results of this experiment are summarized in table 1.

TABLE 1 Acetalization of toluene c.d. conv. Select. c.y. Example Anode % IL electrolyte F [mA/cm²] [%] [%] [%] 1 Graphite 6 MTBS 7 34 65 7 2 2 Graphite 51 MTBS 7 34 88 32 15 3 GDL 12 MTBS 7 34 87 22 9 4 GDL 25 MTBS 7 34 89 29 13 5 Commercial 51 MTBS 8 34 98 45 21 GDL 6 Commercial 51 MTBS 7 34 96 45 23 GDL 7 GDL 51 MTBS 7 34 97 48 25 8 GDL 51 MTBS 6 65 94 49 27 9 Graphite 70 MTBS 6 34 81 30 15 10 GDL 70 MTBS 6 34 93 50 28 11 GDL 70 EMimid- 6 34 98 50 30 TFSI 12 GDL 70 MTB-TFSI 6 34 98 50 32 13 GDL 70 MTB-TFSI 5.5 60 95 54 35

Example 14 for Comparison

In a 100 ml undivided electrolysis cell 6.7 g benzaldehyde dimethylacetal and 37.6 g methanol and 0.45 g sodium bromide (1% by weight) as mediator/supporting electrolyte were electrolyzed for 2.5 F using graphite (10 cm²) as anode and a stainless steel cathode (10 cm²). The applied current density was 34 mA/cm². The GC analysis showed 18% conversion of benzaldehyde dimethylacetal, a selectivity to benzoic acid ortho-ester of 49% and a current yield of 7%.

Example 15 for Comparison

In a 100 ml undivided electrolysis cell 6.1 g benzaldehyde dimethylacetal and 33.9 g methanol and 0.82 g tetrabutyl ammonium bromide (2% by weight) as mediator/supporting electrolyte were electrolyzed for 2.5 F using graphite (10 cm²) as anode and a stainless steel cathode (10 cm²). The applied current density was 34 mA/cm². The GC analysis showed 24% conversion of benzaldehyde dimethylacetal, a selectivity to benzoic acid ortho-ester of 59% and a current yield of 11%.

Example 16

In a 100 ml undivided electrolysis cell 5.2 g benzaldehyde dimethylacetal, 21.2 g methanol, and 23.1 g methyltributylammonium methylsulfate (MTBS, 45% by weight) and 2.2 g tetrabutyl ammonium bromide (4% by weight) as mediator were electrolyzed for 5 F using a GDL (10 cm²) as anode and a stainless steel cathode (10 cm²). The applied current density was 34 mA/cm². The GC analysis showed 72% conversion of benzaldehyde dimethylacetal, a selectivity to benzoic acid ortho-ester of 68% and a current yield of 20%. The GDL electrode has been be manufactured according to U.S. Pat. No. 6,103,077 using carbon black.

Example 17

In a 100 ml undivided electrolysis cell 4.9 g benzaldehyde dimethylacetal, 20.2 g methanol, and 21.8 g methyltributylammonium methylsulfate (MTBS, 42% by weight) and 5.1 g tetrabutyl ammonium bromide (10% by weight) as mediator were electrolyzed for 5 F using a GDL (10 cm²) as anode and a stainless steel cathode (10 cm²). The applied current density was 34 mA/cm². The GC analysis showed 31% conversion of benzaldehyde dimethylacetal, a selectivity to benzoic acid ortho-ester of 83% and a current yield of 10%. The GDL electrode has been be manufactured according to U.S. Pat. No. 6,103,077 using carbon black.

Example 18

In a 100 ml undivided electrolysis cell 5.6 g ethylene carbonate, 27 g pivalic acid and 22.3 g tetraoctylammonium bis(trifluoromethylsulfonyl)imide (41% by weight) as supporting electrolyte were electrolyzed for 4.7 F using a GDL (10 cm²) as anode and a stainless steel cathode (10 cm²). The applied current density was 10 mA/cm². The NMR and GC analysis showed 67% conversion of ethylene carbonate, the yield is 18% of 4-(tert-butyl)carbonyloxy-1,3-dioxolan-2-one. The GDL electrode has been be manufactured according to U.S. Pat. No. 6,103,077 using carbon black. 

1. A process of anodic substitution, the process comprising: b) adding to an electrochemical cell, comprising a cathode and an anode, a liquid reaction medium comprising an organic compound, comprising at least one hydrogen atom bound to a carbon atom, and a nucleophilic agent; and c) electrolyzing the liquid reaction medium to replace at least some hydrogen atoms of the organic compound with a nucleophilic group of the nucleophilic agent, wherein the liquid reaction medium further comprises an ionic liquid in a proportion of at least 10% by weight.
 2. The process of claim 1, wherein the anode is a gas diffusion layer electrode.
 3. The process of claim 2, wherein the gas diffusion layer electrode comprises a substrate and a microporous layer comprising carbon particles as main component.
 4. The process of claim 2, wherein the gas diffusion layer electrode comprises a substrate and a microporous layer comprising carbon black as main component.
 5. The process of claim 1, wherein the ionic liquid comprises an organic cation comprising an ammonium group.
 6. The process of claim 1, wherein the organic compound is selected of the group consisting of (i) an alkane or cycloalkane having at least one hydrogen atom directly bound to a tertiary carbon atom, (ii) an alkene or cycloalkene or diene having at least one hydrogen atom directly bound to an allylic carbon atom, (iii) an alkyarene having at least one hydrogen atom directly bound to a carbon atom in α-position to the arene moiety, (iv) an amide having at least one hydrogen atom directly bound to a carbon atom in α-position to the nitrogen atom, and (v) an ether, ester, carbonate or acetal having at least one hydrogen atom directly bound to a carbon atom in α-position to the oxygen atom.
 7. The process of claim 1, wherein the organic compound is a compound of formula (I):

wherein: X is O, N—R³ or CR⁴R⁵; R¹ is selected from the group consisting of C₁-C₆-alkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl, formyl, C₁-C₆-alkylcarbonyl and C₁-C₆-alkyloxycarbonyl, with the proviso that: if X is a CR⁴R⁵ group then R¹ is optionally C₁-C₆-alkoxy, and if X is a N—R³ or CR⁴R⁵ group then R¹ is optionally C₁-C₆-alkylcarbonyloxy; R² is selected from the group consisting of hydrogen, C₁-C₆-alkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl, C₆-C₁₀-aryl-C₁-C₆-alkyl, C₃-C₁₂-cycloalkyl and C₆-C₁₀-aryl; R³ is selected from the group consisting of hydrogen, C₁-C₆-alkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl, formyl, C₁-C₆-alkylcarbonyl and C₁-C₆-alkyloxycarbonyl; R⁴ and R⁵ are independently selected from the group consisting of hydrogen, C₁-C₆-alkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl and C₁-C₆-alkoxy, or R¹ and R² together with the X—(C═O)—O group to which they are bound form a 5- to 7-membered heterocyclic ring, which optionally comprises at least one additional heteroatom or heteroatom containing group selected from O, S, NR^(c) or C═O, wherein R^(c) is selected from hydrogen, alkyl, cycloalkyl and aryl, or X is a CR⁴R⁵ group and R¹ and R⁴ together with the carbon atom to which they are bound form a 3 to 7 membered carbocyclic ring.
 8. The process of claim 1, wherein the organic compound is a compound of formula (Ia):

wherein: X is O, CH₂ or NR³; R³ is C₁-C₄-alkyl or C₁-C₄-alkylcarbonyl; A is an alkylene group selected from the group consisting of —CH₂—, —CH₂—CH₂—, —CH₂—CH₂—CH₂—, —CHR⁷—, —CHR⁷—CH₂—, —CH₂—CHR⁷—, —CHR⁷—CH₂—CH₂—, —CH₂—CHR⁷—CH₂—, and —CH₂—CH₂—CHR⁷—; R⁷ is C₁-C₆-alkyl; and R⁶ is hydrogen or C₁-C₆-alkyl.
 9. The process of claim 1, wherein the organic compound is a compound of formula (II): Z—CHR⁸R⁹  (II), wherein: Z is selected from the group consisting of C₆-C₁₀-aryl, substituted C₆-C₁₀-aryl, C₁-C₆-allyl, —NR¹⁰R¹¹ group, and C₁-C₆-alkoxy; R⁸ is selected from the group consisting of hydrogen, C₁-C₆-alkyl, and C₁-C₆-alkoxy-C₁-C₆-alkyl, with the proviso that if Z is a C₆-C₁₀-aryl or C₁-C₆-allyl then R⁸ is optionally C₁-C₆-alkoxy, R⁹ is selected from the group consisting of hydrogen, C₁-C₆-alkyl, C₁-C₆-alkoxy, C₁-C₆-alkoxy-C₁-C₆-alkyl, C₆-C₁₀-aryl, substituted C₆-C₁₀-aryl, C₆-C₁₀-aryl-C₁-C₆-alkyl, and C₃-C₁₂-cycloalkyl, or R⁸ and R⁹ together form a C₄-C₇-alkylen or a C₄-C₇-alkenylen, and R¹⁰ and R¹¹ are independently selected from the group consisting of hydrogen, C₁-C₆-alkyl, C₆-C₁₀-aryl, substituted C₆-C₁₀-aryl, and C₁-C₆-alkylcarbonyl, or wherein Z, R⁸ and R⁹ are independently a C₁-C₆-alkyl.
 10. The process of claim 1, wherein the nucleophilic agent is selected from a group consisting of water, an alcohol, a carboxylic acid, nitrous acid or salts thereof, nitric acid or salts thereof, hydrozoic acid or salts thereof, isocyanic acid or salts thereof, isothiocyanic acid or salts thereof, sulfonic acid, isoselenocyanic acid or salts thereof, hydrogen cyanide or salts thereof, hydrogen chloride or salts thereof, hydrogen bromide or salts thereof, and hydrogen iodide or salts thereof
 11. The process of claim 1, wherein the nucleophilic agent is selected from the group consisting of an alcohol of formula (III): R¹²OH  (III), and a carboxylic acid of formula (IV): R¹³COOH  (IV), wherein R¹² and R¹³ are C₁-C₁₂-alkyl or C₁-C₁₂-perfluorinated alkyl.
 12. The process of claim 1, wherein the nucleophillic agent does not include fluorinating agents.
 13. The process of claim 1, wherein the liquid reaction medium further comprises an additive selected from the group consisting of a bromide salt and an iodide salt.
 14. The process of claim 1, wherein the electrochemical cell is an undivided cell.
 15. The process of claim 1, wherein the cathode is selected from the group consisting of Pt, Pb, Ni, graphite, a felt material, stainless steel and GDL electrodes.
 16. A process of manufacturing an acetal of the general formula (VI): Y—C(OR¹²)₂R¹⁴  (VI), from an organic compound of the general formula (V): Y—CH₂R¹⁴  (V), wherein: Y is selected from the group consisting of C₆-C₁₀-aryl, substituted C₆-C₁₀-aryl, C₁-C₆-allyl, and —NR¹⁰R¹¹ group; R¹² is C₁-C₁₂-alkyl or C₁-C₁₂-perfluorinated alkyl; R¹⁴ is selected from the group consisting of hydrogen, C₁-C₆-alkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl, C₆-C₁₀-aryl-C₁-C₆-alkyl, C₆-C₁₀-aryl, substituted C₆-C₁₀-aryl and C₃-C₁₂-cycloalkyl; and R¹⁰ and R¹¹ are independently selected from the group consisting of hydrogen, C₁-C₆-alkyl, C₆-C₁₀-aryl, substituted C₆-C₁₀-aryl, and C₁-C₆-alkylcarbonyl, the process comprising: b) adding to an electrochemical cell, comprising a cathode and an anode, a liquid reaction medium comprising the organic compound of formula (V) and an alcohol of formula (III): R¹²OH  (III), wherein R¹² is C₁-C₁₂-alkyl or C₁-C₁₂-perfluorinated alkyl; and c) electrolyzing the liquid reaction medium to form the acetal of formula (VI) wherein the liquid reaction medium further comprises an ionic liquid in a proportion of at least 10% by weight.
 17. A process of manufacturing an aldehyde or ketone of the general formula (VIa): Y—COR¹⁴  (VIa), starting from an organic compound of formula (V): Y—CH₂R¹⁴  (V), wherein: Y is selected from the group consisting of C₆-C₁₀-aryl, substituted C₆-C₁₀-aryl, C₁-C₆-allyl, and —NR¹⁰R¹¹ group; R¹² is C₁-C₁₂-alkyl or C₁-C₁₂-perfluorinated alkyl; R¹⁴ is selected from the group consisting of hydrogen, C₁-C₆-alkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl, C₆-C₁₀-aryl-C₁-C₆-alkyl, C₆-C₁₀-aryl, substituted C₆-C₁₀-aryl and C₃-C₁₂-cycloalkyl; and R¹⁰ and R¹¹ are independently selected from the group consisting of hydrogen, C₁-C₆-alkyl, C₆-C₁₀-aryl, substituted C₆-C₁₀-aryl, and C₁-C₆-alkylcarbonyl, the process comprising: b) adding to an electrochemical cell, comprising a cathode and an anode, a liquid reaction medium comprising the organic compound of formula (V) and an alcohol of formula (III): R¹²OH  (III), wherein R¹² is C₁-C₁₂-alkyl or C₁-C₁₂-perfluorinated alkyl; c) electrolyzing the liquid reaction medium to form the acetal of formula (VI); and d) hydrolyzing the acetal of formula (VI) to form the aldehyde or ketone of formula (VIa), wherein the liquid reaction medium further comprises an ionic liquid in a proportion of at least 10% by weight.
 18. A process of manufacturing an ortho-ester of formula (VIII): Y—CR¹⁵ ₂(OR¹²)  (VIII), starting from an organic compound of formula (VII): Y—CR¹⁵ ₂H  (VII), wherein: Y is selected from the group consisting of C₆-C₁₀-aryl, substituted C₆-C₁₀-aryl, C₁-C₆-allyl, and —NR¹⁰R¹¹ group; R¹² is C₁-C₁₂-alkyl or C₁-C₁₂-perfluorinated alkyl; R¹⁵ is a C₁-C₁₂-alkoxyl; the process comprising: b) adding to an electrochemical cell, comprising a cathode and an anode, a liquid reaction medium comprising the organic compound of formula (VII), a bromide or iodide salt, and an alcohol of formula (III): R¹²OH  (III), wherein R¹² is C₁-C₁₂-alkyl or C₁-C₁₂-perfluorinated alkyl; and c) electrolyzing the liquid reaction medium to form the acetal of formula (VII), wherein the liquid reaction medium further comprises an ionic liquid in a proportion of at least 10% by weight.
 19. A process of manufacturing an acyloxylated organic compound of formula (Ib):

starting from an organic compound of the formula (Ia):

wherein: X is O, CH₂ or NR³; R³ is C₁-C₄-alkyl or C₁-C₄-alkylcarbonyl; A is an alkylene group selected from the group consisting of —CH₂—, —CH₂—CH₂ ⁻, —CH₂—CH₂—CH₂—, —CHR⁷—, —CHR⁷—CH₂—, —CH₂—CHR⁷—, —CHR⁷—CH₂—CH₂—, —CH₂—CHR⁷—CH₂—, and —CH₂—CH₂—CHR⁷—; R⁷ is C₁-C₆-alkyl; R⁶ is hydrogen or C₁-C₆-alkyl; R¹³ is C₁-C₁₂-alkyl or C₁-C₁₂-perfluorinated alkyl, the process comprising: b) adding to an electrochemical cell, comprising a cathode and an anode, a liquid reaction medium comprising the organic compound of formula (Ia) and an carboxylic acid of formula (IV): R¹³COOH  (IV), wherein R¹³ is C₁-C₁₂-alkyl or C₁-C₁₂-perfluorinated alkyl; and c) electrolyzing the liquid reaction medium to form the acyloxylated organic compound of formula (Ib), wherein the liquid reaction medium further comprises ionic liquid in a proportion of at least 10% by weight. 